In restraining sealed bolted pipe joints of fluid piping systems, a metallic gland and a metallic gripping ring have been used and are being used together to position, to compress, and to seal a gasket about both plastic and metallic pipe. In respect to trying to create excellent seals about both plastic and metallic pipes, when using these metallic gripping rings, difficulties are often encountered. Because there is a limited amount of engaging force created upon the tightening of the bolt and nut fasteners, the gripping ring must have structure that will sufficiently penetrate metallic pipe in creating adequate restraining forces. In contrast, in gripping plastic pipe, which is comparatively weaker, the adequate restraining forces must be spread out through lots of tooth contact area.
In U.S. Pat. No. 4,878,698 of 1989, R. Fowler Gilchrist illustrates and describes his metallic gland and metallic gripping ring used in restraining sealed bolted pipe joints of fluid piping systems, which include both plastic and metallic pipes. The gripping ring utilizes all alike teeth.
Also in respect to the use of plastic pipe in piping systems, Gerald L. Anderson and Phillip E. Frair, in their U.S. Pat. No. 4,569,542 of 1986, illustrated and described how the components of their bolted together, restrained pipe coupling are designed to provide clearance functions, so when the bolt fasteners are tightened, the gasket sealing pressures are achieved about the respective plastic pipe ends sequentially before an effective grip on the respective plastic pipes is attained by the respective lock ring, i.e. grip ring.
These patents and other patents indicate how plastic pipes need differently designed and assembled, sealed, bolted joints, in contrast to sealed bolted joints such as illustrated in U.S. Pat. No. 4,092,036 of 1978, in which Messrs Sato and Edo, illustrated and described their pipe junction holder, which positioned at spaced radial locations about a pipe threaded-bolt-positioned-pipe-pressing members having a pair of edges formed on their bottom end surfaces which gripped the pipe.